Field of the Invention
The present invention relates to a damping force controlling shock absorber, and more particularly, to a damping force controlling shock absorber that is capable of generating a hard damping force when the shock absorber operates at a low speed and controlling an excessive increase of a damping force by preventing a pressure of a back pressure compartment from exceeding a predetermined level even in a driving situation when the shock absorber operates at a medium/high speed.
Description of the Related Art
In general, a shock absorber is installed in means of transportation, such as automobile or the like, and improves a ride comfort by absorbing and damping a vibration or shock from a road surface during driving.
Such a shock absorber includes a cylinder and a piston rod installed to be compressible and extendable within the cylinder. The cylinder and the piston rod are installed in a vehicle body, wheels, or axles.
A shock absorber, a damping force of which is set to be low, can improve a ride comfort by absorbing a vibration caused by unevenness of a rod surface during driving.
On the contrary, a shock absorber, a damping force of which is set to be high, can improve a steering stability by suppressing a change in a posture of a vehicle body.
Therefore, there has been developed a damping force controlling shock absorber in which a damping force controlling valve capable of appropriately adjusting damping force characteristics is mounted on one side, such that the damping force characteristics are appropriately adjusted to improve a ride comfort or a steering ability according to a road surface and a driving condition.
However, if a conventional damping force controlling shock absorber increases a damping force so as to provide a hard damping force, a pressure of a back pressure chamber may exceed a set level in a medium/high speed operating situation, thus lowering the durability of the equipment.
As the prior document related to the present invention, Korean Patent Application Laid-Open No. 10-1998-0002962 (Mar. 30, 1998) discloses a damping force controlling buffer valve.